This invention relates in general to a shock absorber and spring assembly for a vehicle suspension, which assembly is provided with an adjustment device for adjusting the vertical position of the spring and thus controlling the clearance of the vehicle from the ground.

In a vehicle suspension comprising a shock absorber and spring assembly, in which the shock absorber is connected at its lower end to a wheel carrier or to a suspension arm and at its upper end to the body of the vehicle, and in which the spring is arranged around the shock absorber and abuts at its lower end against a spring plate and at its upper end against the body of the vehicle, it is known to use an adjustment device arranged between the cylinder of the shock absorber and the spring plate to vary the vertical position of the spring and thus allow the clearance of the body of the vehicle from the ground to be adjusted.

The adjustment devices used for this purpose may be of different kinds, such as hydraulic devices, pneumatic devices, hydro-pneumatic devices and electromechanical devices. Of these, electromechanical adjustment devices are gaining more and more attention and interest on account of their high level of reliability, their relatively low cost, and their compactness by comparison with other types of adjustment devices.

More specifically, a shock absorber and spring assembly for a vehicle suspension that uses an electromechanical adjustment device comprises an electric motor adapted to generate a rotary motion and a screw and nut screw motion conversion mechanism adapted to convert the rotary motion generated by the electric motor into a translational motion of the spring plate.

The motion conversion mechanism in turn comprises a screw adapted to be rotated about its axis by the electric motor, and a nut screw which meshes with the screw and is connected to the spring plate for conjoint translation therewith, in such a way that, by activating the electric motor, the rotary motion transmitted by the electric motor to the screw is converted into translational motion of the nut screw, and thus into translational motion of the spring plate.

A solution of the type mentioned above is known, for example, from PCT/IB2018/059025, which discloses a spring and shock absorber assembly for a vehicle suspension, which assembly is designed to prevent the spring plate from rotating relative to the shock absorber without needing to use suitable anti-rotation means.

In this known solution, the screw and the nut screw of the motion conversion mechanism are arranged eccentrically with respect to the axis of the shock absorber, and the kinematic mechanism formed by the worm screw and by the nut screw is designed to have low efficiency (i.e. high levels of friction) such that it is an irreversible mechanism.

In so doing, the screw is only allowed to rotate relative to the nut screw when the former is rotated by the electric motor, whereas rotation caused solely by the downward forces transmitted by the spring to the spring support plate is prevented.

Ultimately, this solution ensures that the mechanism is not able to move from a particular attained position, due solely to the effect of the weight of the vehicle and the other resilient forces caused by the deformation of the spring when the vehicle is in use.

However, this solution has some disadvantages caused by the high friction of the screw/nut screw kinematic mechanism, such as the high electrical energy consumption by the electric motor (since it is necessary to expend a lot of energy to counteract the friction forces), long activation times (since a considerable part of the power input to the electric motor is used to counteract the friction, and is therefore not used to move the spring support plate vertically), and high wear of the screw and nut screw threads (the tangential force components on the threads are higher, resulting in the device having a shorter service life). Summary of the invention

The object of this invention is to overcome the aforementioned problems.

To achieve this object, a spring and shock absorber assembly for a vehicle suspension according to the invention comprises an additional mechanism for blocking the relative rotation between the screw and the nut screw, which is necessary in order to be able to maintain the desired position of the spring support plate under the action of the forces transmitted to the spring by said plate without having to continue to supply the electric motor with electricity, even when a high-efficiency, i.e. reversible, screw/nut screw kinematic mechanism is used.

The electromechanical adjustment device according to the invention comprises: an electric motor adapted to generate a rotary motion; a motion conversion mechanism which extends along an axis parallel but not coincident to the axis of the shock absorber and which in turn includes a nut screw which meshes with a screw rotated by the electric motor, which nut screw is connected to the spring support plate for conjoint translation therewith; and a mechanism for blocking the rotation of the screw with respect to the nut screw, comprising a clutch, the opening action of which is controlled by exciting an electromagnet with electrical current. The screw/nut screw kinematic mechanism is preferably high-efficiency, for example is achieved by the use of a ball screw.

The mechanism for blocking the rotation of the screw with respect to the nut screw comprises an electrically actuated clutch which includes two discs provided with profiles which mesh with one another, i.e. a lower disc which rotates together with the screw, and an upper disc which is non-rotatably fixed but is able to translate axially along the axis of the screw.

According to one embodiment, on the two faces facing one another, the two discs have a series of teeth which may engage with one another. These teeth may have profiles which, with respect to a plane containing the axis of the screw, form different angles on their right-hand side and on their left-hand side, i.e. depending on the engaged flank. In particular, when the screw tends to rotate in a first direction, the two engaged teeth are brought into contact with one another on a first side, which is advantageously characterized by a small angle of the profile of the teeth with respect to a plane containing the axis of the screw, and the sliding of a tooth of the upper disc with respect to the tooth of the lower disc is therefore blocked, thus also preventing the screw from rotating with respect to the nut screw and preventing the upward translation of the upper disc.

By contrast, when the screw tends to rotate in a second direction counter to the first direction, the two engaged teeth are brought into contact with one another on a second side, which is advantageously characterized by a large angle of the profile of the teeth with respect to a plane containing the axis of the screw, and it is therefore possible to slide a tooth of the upper disc with respect to the tooth of the lower disc, thus making it possible to rotate the screw with respect to the nut screw and consequently translate the upper disc upward.

The first direction of rotation corresponds to the direction of rotation of the screw during the downward motion of the spring support plate. This downward motion is triggered by the downward force transmitted by the spring to the spring support plate.

By contrast, the second direction of rotation corresponds to the direction of rotation of the screw during the upward motion of the spring support plate. This upward motion is only possible when the screw is activated by the electric motor.

The upper disc is preferably pushed downward by resilient return means, in so doing ensuring that the profiles of the upper disc enter into engagement with the profiles of the lower disc. The upper disc may also be moved upward by using an electrical current to excite an electromagnet arranged above the upper disc. By exciting the electromagnet, the upper disc is attracted and is translated upward until the teeth of the upper disc are no longer engaged with the teeth of the lower disc. In this latter condition, the mechanism is unblocked and the screw may freely rotate in one direction of rotation or in the other direction of rotation under the action of the torque transmitted by the electric motor, or under the action of the downward force transmitted by the spring through the spring support plate, or as a result of both of these two actions combined.

The aforesaid and other aims and advantages are achieved, according to one aspect of the invention, by a spring and shock absorber assembly for a vehicle suspension and by a method for moving the spring plate of a shock absorber which have the features defined in the accompanying claims.

Brief description of the drawings

The functional and structural features of some preferred embodiments of a spring and shock absorber assembly for a vehicle suspension according to the invention will now be described. Reference is made to the appended drawings, in which:

- Fig. 1 is a schematic perspective view of a spring and shock absorber assembly for a vehicle suspension, according to one embodiment of the invention;

- Fig. 2 is a schematic axial cross-sectional view of the spring and shock absorber assembly for a vehicle suspension in Fig. 1;

- Fig. 3 is a schematic axial cross-sectional view of a detail in Fig. 2, in particular the mechanism for blocking the rotation of the screw;

- Fig. 4A and 4B are two schematic perspective views of a mechanical clutch associated with the mechanism for blocking the rotation in Fig. 3, in a condition in which the respective profiles are engaged and in a condition in which the respective profiles are disengaged, respectively, according to one embodiment of the invention; and

- Fig. 5A and 5B are schematic side views of the mechanical clutch in Fig. 4A and 4B shown in respective conditions in which the profiles are engaged on opposite sides of the teeth, according to one embodiment of the invention.

Detailed description

Before describing in detail a plurality of embodiments of the invention, it should be clarified that the invention is not limited in its application to the design details and configuration of the components presented in the following description or illustrated in the drawings. The invention is capable of assuming other embodiments and of being implemented or constructed in practice in different ways. It should also be understood that the phraseology and terminology have a descriptive purpose and should not be construed as limiting.

With reference made by way of example to Fig. 1 to 3, a shock absorber and spring assembly for a vehicle suspension according to this invention comprises a shock absorber 10 having a cylinder 14 and a rod 16 which extend along a first axis z, and a spring plate 18 which is arranged around the cylinder 14 of the shock absorber 10 and is slidable with respect thereto along said first axis z.

The following are also present: a spring 12, the bottom of which rests on the spring plate 18; and an electromechanical adjustment device arranged between the cylinder 14 of the shock absorber 10 and the spring plate 18, for varying in a continuous and controlled manner the vertical position of the lower end of the spring 12 and thus allowing the clearance of the vehicle from the ground to be adjusted.

This adjustment device comprises an electric motor 22 adapted to generate a rotary motion, and a screw and nut screw motion conversion mechanism 24, 26 adapted to convert the rotary motion generated by the electric motor 22 into a translational motion of the spring plate 18, wherein said motion conversion mechanism comprises a single screw 24 which extends along a second axis z’ parallel to said first axis z and is adapted to be rotated by the electric motor 22 about said second axis z’, and a single nut screw 26 which meshes with the screw 24 and is connected to the spring plate 18 for conjoint translation therewith, in such a way that, following the activation of the electric motor 22, the rotary motion transmitted by the electric motor 22 to the screw 24 is converted into translational motion of the nut screw 26 along said second axis z’, and therefore into translational motion of the spring plate 18 with respect to the cylinder 14 of the shock absorber 10 along said first axis z.

The second axis z’ is spaced from said first axis z in such a way that the unit formed by the screw 24 and the nut screw 26 is arranged eccentrically with respect to the cylinder 14 of the shock absorber 10 and to the spring plate 18. The motion conversion mechanism further comprises a mechanism for blocking the rotation of the screw 24, which blocking mechanism includes a primary disc 50 which is connected to the screw 24 for conjoint rotation therewith, and an auxiliary disc 52 which is non-rotatably fixed with respect to the screw 24, the primary and auxiliary discs having respective profiles 50’, 52’ which mesh with one another.

The auxiliary disc 52 is movable along the axis z’ from a blocking position (a lower position in the example shown) in which the profiles 50’, 52’ of the two primary 50 and auxiliary discs 52 are mutually engaged and the rotation of the screw 24 is prevented, and an unblocking position (an upper position in the example shown) in which the profiles 50’, 52’ of the two primary 50 and auxiliary discs 52 prevent mutual engagement and the rotation of the screw 24 is allowed.

According to one embodiment, the shock absorber and spring assembly for a vehicle suspension also comprises a first support arm 28 which carries the electric motor 22 and the screw 24 and is rigidly connected to the cylinder 14 of the shock absorber 10, a second support arm 34 which carries the nut screw 26 and is rigidly connected to the spring plate 18, and a guide sleeve 38 which is rigidly connected at one end to said second support arm 34 and at the other end to the spring plate 18 and is arranged around the cylinder 14 of the shock absorber 10 so as to be able to slide along the first axis z.

The mechanism for blocking the rotation of the screw 24 may advantageously be housed in a seat provided in the first support arm 28.

According to one preferred embodiment, the mechanism for blocking the rotation of the screw 24 comprises an electromagnet 58 adapted to attract the auxiliary disc 52 toward the unblocking position by means of electrical excitation, and resilient means 56 adapted to push the auxiliary disc 52 toward the blocking position.

According to one embodiment, the mutually meshing profiles 50’, 52’ comprise respective teeth having a first side which has a first angle with respect to a plane containing the axis z’ and which enters into engagement when the screw 24 rotates or tends to rotate in a first direction of rotation (advantageously when the spring plate 18 tends to move downward along the first axis z), and a second side which has a second angle with respect to a plane containing the axis z’ that is greater than the first angle, said second side entering into engagement when the screw 24 rotates or tends to rotate in the opposite direction of rotation (advantageously when the spring plate 18 tends to move upward along the first axis z). This first direction of rotation and second direction of rotation may be, for example, a counterclockwise direction of rotation and a clockwise direction of rotation of the discs, respectively, as shown in Fig. 4A and 4B.

The first angle is preferably between 5° and 15° so that the sliding of the profile of the auxiliary disc 52 with respect to the profile of the primary disc 50 is blocked, and the second angle is between 65° and 75° so that it is possible for the profile of the auxiliary disc 52 to slide with respect to the profile of the primary disc 50. This configuration makes it possible to impart an initial course to the auxiliary disc 52 along the second axis z’, by virtue of the mutual sliding of the profiles having the second angle. In this way, it is possible, for example, to move the auxiliary disc 52 closer to the possible electromagnet 58, thus reducing the excitation energy required to attract the auxiliary disc 52 toward the position of disengagement from the primary disc 50.

The first side preferably enters into engagement when the screw 24 rotates or tends to rotate so as to cause a descending motion of the nut screw 26 along the axis z’, and the second side enters into engagement when the screw 24 rotates or tends to rotate so as to cause an ascending motion of the nut screw 26 along the axis z’.

According to one preferred embodiment, the screw 24 is a ball screw. A high-efficiency kinematic mechanism is thus obtained, reducing the friction and increasing the energy efficiency of the assembly.

The adjustment device may advantageously also comprise a speed reduction gear mechanism arranged between the electric motor 22 and the screw 24. According to one aspect of the invention, a method for moving the spring plate 18 of a shock absorber 10 comprises the steps of providing a shock absorber and spring assembly for a vehicle suspension according to one or more of the embodiments described above.

The mechanism may be activated downward by means of the following steps. Starting from the condition in which the mechanism for blocking the rotation of the screw 24 is in the blocking position, in which the profiles 50’, 52’ of the two primary 50 and auxiliary discs 52 engage with one another (being advantageously engaged with one another on the first side, which does not allow relative sliding between the engaged teeth, or on the side of their first angle), the electric motor 22 is activated in the second direction of rotation until the teeth come into contact with each other on the second side (side of their second angle), which instead allows the relative sliding between the two engaged profiles.

The electric motor 22 is then made to continue to rotate in the second direction of rotation so that, by means of the relative sliding of the engaged teeth, the primary disc 50 rotates further with respect to the auxiliary disc 52, triggering a translation of the latter along the axis z’ away from the primary disc 50.

The electromagnet 58 is then excited so as to further attract the auxiliary disc 52 along the axis z’ until the profiles of the primary and auxiliary discs 50, 52 disengage from one another and the mechanism for blocking the rotation of the screw 24 unblocks, and the rotation of the electric motor 22 in the second direction of rotation is stopped so that, for example under the action of the downward force transmitted by the spring 12 through the spring plate 18, the screw 24 rotates in the first direction of rotation and the spring plate 18 moves downward along the first axis z, keeping the electromagnet 58 excited.

Once the spring plate 18 has reached the desired position along the axis z, the electromagnet 58 is de-excited, and the profiles of the two primary and auxiliary discs 50, 52 are brought back into engagement (advantageously on account of the action of the resilient means 56) and into contact with one another on their first side by the action of the downward force transmitted by the spring 12, causing the rotation of the device to be blocked. From this moment on, the vertical position of the spring plate 18 remains unchanged.

Given that the electromagnet 58 is preferably configured to operate on the principle of reluctance, it is possible to estimate the position of the auxiliary disc 52 with respect to the primary disc 50 by means of measuring the inductance of the magnetic circuit.

Similarly, the mechanism may be activated upward by means of the following steps. Starting from the condition in which the blocking mechanism is engaged and the teeth of the two discs 50, 52 are therefore in contact on the first side, which does not allow relative sliding between the engaged teeth, the electric motor 22 is activated in the second direction of rotation until the teeth come into contact on the opposite side (second side), which allows the relative sliding between the two engaged profiles. The motor 22 continues to rotate in the second direction of rotation and, on account of the relative sliding of the engaged teeth, the primary disc 50 may also rotate with respect to the auxiliary disc 52 and this latter begins to translate upward. At this point, the electromagnet 58 of the blocking device is excited and a further action is exerted on the auxiliary disc 52, which action also translates said auxiliary disc upward until the teeth of this auxiliary disc 52 are no longer engaged with the teeth of the primary disc 50, and the mechanism unblocks. Starting from this condition, the electric motor 22 continues to be controlled in the second direction of rotation, causing the spring plate 18 to ascend. During the entire ascension phase, the electromagnet 58 is kept excited. Once it has reached the desired position, the electric motor 22 is de-energized and the electromagnet 58 is de-excited, and the profiles of the two primary and auxiliary discs 50, 52 are brought back into engagement (advantageously on account of the action of the resilient means 56) and into contact on their first side by the action of the downward force transmitted by the spring 12, causing the rotation of the device to be blocked. From this moment on, the vertical position of the spring plate 18 remains unchanged.

Throughout this description and in the claims, the terms and expressions indicating positions and orientations, such as “axial” or “transverse,” refer to the first axis z and the second axis z’ . Various aspects and embodiments of a spring and shock absorber assembly for a vehicle suspension and a method for moving the spring plate of a shock absorber according to the invention have been described. It is understood that each embodiment may be combined with any other embodiment. Furthermore, the invention is not limited to the described embodiments, but may be varied within the scope defined by the appended claims.